Yesterday I spotted a video submitted to Hacker News by the Polish startup Killswitch.me that clearly showed sending a link in a Facebook private message increases the Like counter on the link’s originating third-party website. This would suggest Facebook is scanning your private messages for shared links to Web pages with Like buttons, so it can increase the number of corresponding Likes for those pages. Facebook confirmed this information with me today, though it did emphasize this only happens for third-party websites with Facebook plugins, not Facebook Pages.

The original video included NSFW imagery and was promptly taken down by YouTube (for reference, it’s still up on Vimeo). In addition to the potential privacy problems of performing such scans, the short clip also showed a curious oddity: when Facebook detects a link to a “Likeable” page, it increases the counter by two Likes.

Facebook sent me the following statement about this issue today:

We did recently find a bug with our social plugins where at times the count for the Share or Like goes up by two, and we are working on fix to solve the issue now. To be clear, this only affects social plugins off of Facebook and is not related to Facebook Page likes. This bug does not impact the user experience with messages or what appears on their timelines.

I had to clarify something though. Was the bug in question the fact that the counter goes up by two, or the fact that the counter goes up in the first place, when links are shared privately? The Facebook spokesperson told me that it was indeed the fact that it went up by two. In other words, Facebook is monitoring your private messages for links that have Like buttons and should be increased.

This is news to me. Yet this was clearly the case before as on the Like button Web page over on Facebook Developers, the social networking giant says the number shown on a Like button is the sum of:

The number of likes of this URL.

The number of shares of this URL (this includes copy/pasting a link back to Facebook).

The number of likes and comments on stories on Facebook about this URL.

The number of inbox messages containing this URL as an attachment.

I’ve known for a while that the Like button isn’t a counter of just Likes: it also includes Shares as well as comments on Liked and Shared items on the social network. Private messages, however, are something completely different, and they have privacy questions attached to them.

The most important one: if I use Facebook to privately share a link (especially if it’s to something controversial), and the company increases the Like counter, will the Like button on that site show my name to my Facebook friends who also visit that site? I don’t expect anything to show up on my Timeline, but maybe on the site itself, since Facebook already does this for things I actively hit the Like button for.

Thankfully, this isn’t the case. When I asked for clarification, Facebook sent along this statement:

Absolutely no private information has been exposed and Facebook is not automatically Liking any Facebook Pages on a user’s behalf.

Many websites that use Facebook’s ‘Like’, ‘Recommend’, or ‘Share’ buttons also carry a counter next to them. This counter reflects the number of times people have clicked those buttons and also the number of times people have shared that page’s link on Facebook. When the count is increased via shares over private messages, no user information is exchanged, and privacy settings of content are unaffected. Links shared through messages do not affect the Like count on Facebook Pages.

Well, there’s another privacy disaster avoided. Facebook seems to have to deal with this type of thing every week.

Update at 4:55PM EST: Facebook got in touch again to further explain the situation. Here’s what’s happening: “Our systems parse the URL being shared in order to render the appropriate preview, and to also ensure that the message is not spam.”